Extensive research activities have been directed in order to provide immobilized lipase preparation, in consideration of the growing use for immobilized lipases to interesterification. Some of the first industrially applicable immobilized lipase preparations for interesterification are described in U.S. Pat. No. 4,275,081, col. 7, lines 28-35, from which it appears that the immobilized lipase preparations are prepared by acetone precipitation of an aqueous lipase solution on Celite.RTM. diatomaceous earth.
However, the half life of these immobilized lipase preparations are relatively low. Also, the obtainable specific lipase activity is relatively low. Furthermore, a dust problem during storage and loading into the columns is present, and also, solvents are necessary during use of these prior art immobilized lipase preparations.
Thus, the research activities have more or less been focused on immobilization of lipase on carriers with hydrophobic binding sites. Reference can be made to Biotechnology and Bioengineering, Vol. XXIV, pp. 1007-1013 (1982), from which it appears that it is generally assumed that in the preparation of immobilized lipase preparations with high half life and high activity for industrial applications a carrier with hydrophobic binding sites more or less was a conditio sine qua non. Also, reference is made to published Danish patent No. 152763, which describes an immobilized lipase preparation with a carrier consisting of a particulate macroporous weak anion exchange resin, e.g. a resin belonging to the Duolite.RTM. series. Carrier resins of this kind have hydrophobic binding sites, and the preparations exhibit a high half life and are very well suited for industrial interesterification.
Even so, however, these anion exchange resins do have drawbacks. In the first place they are very expensive, and this has a great bearing on the price of the immobilized lipase preparations. In the second place it has been found that during use in organic media extractables from the anion exchange resins are transferred to the organic medium, and even if the amount of the extractables is low, this often represents a serious disadvantage, especially if the end product of the enzymatic process is intended for human consumption. It is possible to wash the resins with organic solvents prior to immbilization, but this is a costly step.
Thus, a need exists for a cheap immobilized lipase preparation with high half life and possibility of high specific activity and without any possibility for transfer of extractables from the carrier to an organic phase.